Detailed Mathematical Analysis of a Class of Covert Channels Arising in Certain Anonymizing Networks

摘要

There have long been threads of investigation into covert channels, and threads of investigation into anonymity, but these two closely related areas of information hiding have not been directly associated. This report represents an initial inquiry into the relationship between covert channel capacity and anonymity, and poses more questions than it answers. Even this preliminary work has proven difficult, but in this investigation lies the hope of a deeper understanding of the nature of both areas. Mixes have been used for anonymity, where the concern is shielding the identity of the sender or the receiver of a message, or both. Traffic analysis prevention (TAP) methods are used to conceal larger traffic patterns. Here, we are concerned with how much information a sender to a Mix can leak to an eavesdropping outsider, despite the concealment efforts of Mixes acting as firewalls.